The Dawning of Natural Language Parsers
and Interactive Fiction

An important development that made Colossal Caves possible was the natural language parser. This was created by Joseph Weizenbaum at MIT during the years 1964-1966 for his program ELIZA [Wei66]. ELIZA was created to simulate a Rogerian psychotherapist (Weizenbaum 1966). The program prompts who ever is at the keyboard to say something about themselves. It then uses a natural language parser which searches for certain key words, these indicate which phrases the computer uses in reply, then it formulates its response using some of those key words. In this way it "holds a conversation".

What this meant to Colossal Caves is that it expanded the field of interactivity. Not only could the audience direct the computer to display text about what they might find if they go left or right down a forking path, if the audience found described on their path a bag full of rubies, they could type in instructions such as "pick up the rubies" or "throw the rubies at the monster" and the natural language parser would make it possible for the computer to give an appropriate response to these instructions. This immensely increased the audience's ability to ``live'' in the world of the story, giving them something they could not experience in any other medium.

Colossal Caves was closely followed by Adventureland in 1978 by Scott Adams which he used to found his computer game company, Adventure International [Ada96]; Zork in 1980 by Dave Lebling, Marc Blank, Bruce Daniels, and Tim Anderson, which led to the founding of Infocom [AG85]; and Mystery House in 1980 by Roberta and Ken Williams was used to found what eventually became Sierra On-line [Wil98].

The game Hitch Hiker's Guide to the Galaxy [AM84] made extensive use of the natural language parser, in order that readers might have conversations with many of the characters from the original series of novels by Douglas Adams. This game established Infocom as an ongoing computer entertainment company. Douglas Adams was so impressed with this ability to chat with the natural language parser that he went back to use it even more extensively in his game Starship Titanic [Ada98a].

Text based interactive fiction continues to be written today and with twenty years of experience, its creators really know how to make branching storytelling work. I can highly recommend checking out the IF archives at http://www.wurb.com/if/index.html. Interactive fiction's development was crucial to the eventual addition of colour graphics (as opposed to vector graphics), animation and eventually live-action sequences, as the early IF companies sought to maintain their audience's interest by expanding into new forms of adventure gaming.